The instant invention relates to an apparatus for cooling water, especially in cooling towers, comprising a wet cooling portion in which the water which trickles down and is to be cooled is contacted directly with air flowing by, and a dry cooling portion in which the water is separated by walls from the air flowing by.
In conventional wet cooling towers the trickler plates are normally oriented with their width in vertical direction and cooling water is sprayed on both surfaces and then trickles down. The water is exposed to the air flowing by in upward direction at both sides of the trickler plate and is thereby cooled. Because of the direct contact of the water with the air on both sides of the trickler plates a considerable portion of the cooling water evaporates and is discharged from the cooling tower in the form of vapour clouds. Apart from the loss of water this has undesired ecological influences.
Other prior art wet cooling towers such as that disclosed in the Copeland U.S. Pat. No. 3,669,425 dated June 13, 1972, recognize the misting problems and employ mist eliminators or baffles to reduce water loss by the centrifugal forces generated by sharp deflections in the air flow.
Also dry cooling towers are known with which the cooling water is not directly contacted with the air but instead is passed through finned tubes or the like. Such finned tubes are expensive. Besides, the cooling performance is much poorer than with wet cooling towers because no evaporation of water takes place.
Cooling towers of the type mentioned above have been proposed, which incorporate both wet cooling and dry cooling portions in the one tower, separate air streams flowing past the respective wet and dry cooling portions.
An object of the present invention is to produce an apparatus of the type specified which will provide an excellent combination of the advantages of wet and dry cooling, with good mixing of the wet and dry air streams, and which will be simple and economical to manufacture.
Accordingly, it is an object of the instant invention to provide a novel method and cooling tower which has a much simpler structure than those generally known.
It is a further object of the instant invention to provide a novel method and cooling tower with an optimum combination of the advantages of wet cooling and dry cooling in the same vertical space.
It is still a further object of the invention to provide a novel method and cooling tower with good mixing of the wet and dry air streams.
To meet these and other objects which will become apparent as the description proceeds it is provided, in accordance with the invention, that trickler plates which are essentially wetted on one side form the wet cooling portion with their wetted sides, while their dry sides form the dry cooling portion, and each duct formed between two adjacent trickler plates being bounded on one of its sides by a wet face of a trickler plate and on its opposite side by the oppositely-facing dry face of an adjacent plate, namely the trickler plates, with wet cooling elements and dry cooling elements in alternating arrangement.
With the apparatus according to the invention, the cooling water which has become heated and is to be cooled again impinges only on one side of the trickler plates and consequently also runs down only on one side. The other side, i.e., the opposite surface, remains essentially dry. The result thereof is that a considerably smaller water surface is exposed directly to the air and consequently subjected to wet cooling. The air flowing by along the other dry surface of each trickler plate effects cooling in the same way as with the dry cooling process.
Without any additional device this arrangement warrants good mixing above the trickler plates of the "wet" and "dry" air streams which flow in parallel through the wet cooling elements and through the dry cooling elements, the structure practically causing no more expenditure than the conventional wet cooling towers.
This makes it possible to diminish the disadvantages of dry cooling and wet cooling and to combine the advantages of these two cooling processes. The expensive finned tubes or the like, normally required for dry cooling, are not necessary. Instead the trickler plates may consist of a single wall and be given their necessary configuration simply by an inclined arrangement or by bending. This is very little additional expenditure in manufacture as compared to the vertical trickler plates used in wet cooling towers.
The desired effect can be obtained merely by an appropriate configuration of the trickler plates, by arranging them at an angle with respect to the vertical at least in an area in which the cooling water impinges on the trickler plates.
In this context it should be especially noted that the trickler plates may be made from thin-walled material such as sheet metal or plastics so that much lighter structures can be obtained in comparison with finned tube structures. This fact also reduces the expenditure for the carrier structure of the trickler plates.
The trickler plates may be formed with bulges on their "wet side" in order to reduce the wet cooling surface still more.
If the trickler plates are directly exposed to the cooling water which is sprayed down upon them, wetting of the underside of the inclined section cannot be prevented, although with a minor portion of the water. As a remedial measure a preferred modification of the apparatus according to the invention provides for the arrangement of plane or corrugated (for greater rigidity) and essentially vertically oriented alignment plates above the trickler plates. Conveniently, these alignment plates are of lesser height than the trickler plates and cause drops to fall only in vertical direction on the inclined sections of the trickler plates. Also the alignment plates may be inclined with respect to the vertical, at least in the area on which the cooling water impinges.
The exclusive wetting of one side of the trickler plates is completely guaranteed if the lower ends of the alignment plates are laterally offset with respect to the upper ends of the trickler plates.
The trickler plates themselves may be designed differently within the scope of the invention. In a particularly simple embodiment the upper sections of the trickler plates are bent over smoothly or sharply relative to the lower vertical sections.
The trickler plates may also be inclined over their entire height and may be provided in their upper sections with dripping noses pointing downwardly and being interconnected by guide means guiding the trickling water towards their points. The guide means may be embodied simply by curved bending lines in the sheet metal of the trickler plates, the lowermost ends of these bending lines terminating in these dripping noses. With this type of design the alignment plates may be eliminated altogether because cooling water sprayed on the undersides of the trickler plates is caught already in the upper area at the dripping noses and is led off along the upper side.
It is also an object of the instant invention to vary the proportions between wet cooling and dry cooling. In a first embodiment of the invention to meet this object the trickler plates can be pivoted from their vertical position in which their upper ends are aligned with the lower ends of the alignment plates into a position in which their upper ends are disposed between the lower ends of the alignment plates.
In a second embodiment in which the upper ends of the trickler plates are vertically oriented the variation can be obtained by either pivoting the alignment plates with their lower ends out of a position of alignment with the upper ends of the trickler plates into an intermediate position or by displacing the alignment plates in parallel relative to the trickler plates or vice versa.
The desired effect of the invention can also be obtained by appropriate configuration of the spray device alone. To this end a further embodiment of the invention provides for the spray plane of the water discharged from the spray device to be inclined with respect to the vertical.
Also in this case the proportions of wet cooling and dry cooling can be varied by changing the inclination of the spray plane by mechanical adjustment of the spray device about a horizontal axis or by changing the cooling water inlet pressure.
The designs according to the invention of the trickler plates and of the spray device may also be used in combination. Alignment plates may be eliminated altogether if trickler plates which are inclined at least in their upper sections are used in combination with the inclined spray planes.